The standard mechanism for selective engagement of the barrel portions of writing instruments consists of a male threaded end of one of the barrel portion and a complementary female threaded end of the other barrel portion. A user must impart at least one 360° revolution, and, more typically, several revolutions, of one of the barrel portions relative to the other in order to separate the two barrel portions for the purpose of gaining access to an ink retaining reservoir stored therein, such as for purposes of replacement of a low ink cartridge. In order to securely re-engage the two barrel portions, the user must again impart at least one 360° revolution, and, more typically, several revolutions, of one of the barrel portions relative to the other.